Traits

Eyes that are tightly shut. 

The shut eye trait occurs for a variety of reasons from mimicry to an underdeveloped eyeball to light sensitivity.  Whatever the cause, these leeches like to keep their eyes closed, and either have very poor eyesight or none at all! 

A type of eye that is characteristically small, round and pupil-less. 

Bead-eyed leeches are generally masters of hiding their eyes in plain sight, as they are often small and easily mistaken for natural markings or gemstones.  These eyes are still soft and will upset the leech if poked, so care must be taken to notice where they are on the leech when petting!

Middle-sized expressive eyes, often used as a catch-all term for eyes that are not any of the other types.

Mammalian eyes can be any shape and color, and may or may not have pupils, but always feature points at either end similarly to our own.  The strength of the eyesight varies from leech to leech and is also tied to its placement on the body.

An unusual eye type that is solid like a marble and often feature exquisite designs and patterns on their surface.
Their notable feature is the ability to appear elsewhere on the body, as long as an eye socket is present. In this sense, each socket counts as an eye regardless of actual eyes present, and more than five is considered a myth trait. 

The leech carefully guards these travelling eyes as losing one out of the body is exceptionally painful, and immediately results in blindness of that eye. Once a See-all eye stops functioning, the leech will abandon it without exception; this is usually the reason for a leech having fewer eyes than number of sockets. 

In collectors' circles, removed see-all eyes are incredibly valuable, resulting in high rates of poaching for these beautiful items - especially since it is randomly-occurring and cannot be bred. 

Note: See-all eyes cannot be held in the mouth or by the tongue; this is considered retired. Any leech with this presentation cannot maintain it through a redesign. 

In rare cases a leech may develop a surplus of eyes, exceeding the standard maximum of five. 

These eyes can be any eye trait, color, shape and size, and can appear clustered or spread across the body.  It is considered a genetic mutation more than anything else and often creates some interesting results.

Note:  They have to be separate sets of identifiable eyes, and listed accordingly.  These eyes can all be the same type, or different. 

Narrow slit-looking eyes, usually without a pronounced pupil. 

A close variant of shut eyes, but for whatever reason the leech cannot keep them closed all the way. These leeches still tend to have poor eyesight, but the trait is popular on pets to give the appearance of smiling very hard. 

Sightless eyes with a pale pupil.
Cave leeches are inherently blind, though some have developed eyes as a mimic target. On occasion these eyes can detect changes in light and dark - but without evolved optic nerves they're still functionally useless.

Note: Cave leeches cannot have any other eye type - but these can take the shape of all other eyes. The important part for them is that they are blind, even see-all shaped false eyes!